as in treacherous
formal
causing harm in a way that is gradual or not easily noticed
Most people with this insidious disease have no idea that they are infected. an insidious enemy
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Recent Examples of insidious
After all, offenses committed by individuals in positions of public trust are especially insidious.
—
Craig MacLellan, Boston Herald, 3 Apr. 2026
The trailer released this week (below) shows the gang during happier times in 1985 — before the latter seasons would introduce villain Vecna (played by Jamie Campbell Bower in the original series) and an even more insidious era of the Upside Down.
—Jackie Strause, HollywoodReporter, 27 Mar. 2026
Now’s the time to review all your spending — especially your subscriptions, which suddenly become insidious charges that feel like insult to injury.
—Harlan Vaughn, CNBC, 23 Mar. 2026
In the face of the insidious chaos of 2026, the band rises to the moment with A Wave That Will Never Break, an ecstatic, devotional album stocked with powerful choruses that reflect on the nature of destruction.
—Nina Corcoran, Pitchfork, 23 Mar. 2026
See All Example Sentences for insidious
Craig MacLellan, Boston Herald, 3 Apr. 2026
The trailer released this week (below) shows the gang during happier times in 1985 — before the latter seasons would introduce villain Vecna (played by Jamie Campbell Bower in the original series) and an even more insidious era of the Upside Down.
—Jackie Strause, HollywoodReporter, 27 Mar. 2026
Now’s the time to review all your spending — especially your subscriptions, which suddenly become insidious charges that feel like insult to injury.
—Harlan Vaughn, CNBC, 23 Mar. 2026
In the face of the insidious chaos of 2026, the band rises to the moment with A Wave That Will Never Break, an ecstatic, devotional album stocked with powerful choruses that reflect on the nature of destruction.
—Nina Corcoran, Pitchfork, 23 Mar. 2026
See All Example Sentences for insidious
Recent Examples of Synonyms for insidious
Adjective
-
Ships have increasingly traveled through the Panama Canal as shipments are rerouted and buyers purchase from other countries to avoid commerce through now-treacherous Middle Eastern waterway.—
Alma Solis,
Fortune,
24 Apr. 2026
-
Ben hunts, and Sasha tries to survive, not just him but various treacherous and dangerous elements that make that mountain climb at the start look like kids play.—
Pete Hammond,
Deadline,
23 Apr. 2026
Adjective
-
And according to therapists, that distinction can be subtle but significant, often showing up in patterns that feel normal on the surface but are actually rooted in the need to feel chosen rather than the desire to truly know someone.—
Hana Hong,
SELF,
22 Apr. 2026
-
The final drink had a subtle floral note with a hint of cinnamon that reminded me of horchata.—
Tristan Graziano,
Charlotte Observer,
22 Apr. 2026
Adjective
-
But that confidence could harbor false hope, says Kelly Richardson, principal of Richardson Ober LLP, a California law firm known for offering community association advice, and a monthly contributing writer to the Southern California News Group.—
Amancai Biraben,
Oc Register,
24 Apr. 2026
-
The indictment also charges Meade and West each with one count of conspiracy to obstruct and defeat the Internal Revenue Service, five counts of attempts to interfere with administration of internal revenue laws and seven counts of aiding or assisting the filing of false documents, officials said.—
Justin Muszynski,
Hartford Courant,
24 Apr. 2026
Adjective
-
The suit alleges negligence, personal injury and deceptive business practices.—
Laura Bauer,
Kansas City Star,
22 Apr. 2026
-
Barrera played Michelle, a deceptive character who will keep everyone guessing.—
Denise Petski,
Deadline,
15 Apr. 2026
Adjective
-
The government took a genuine invitation to collaborate as a perfidious power grab.—
Gideon Lewis-Kraus,
New Yorker,
14 Mar. 2026
-
For those trying to read Iran’s future, the lesson of 1953 is not just that foreign powers can be perfidious.—
Bobby Ghosh,
Time,
5 Mar. 2026
Adjective
-
Intelligence is basically anything with a pretty clear definition between the set of correct and incorrect answers—think tasks in coding, mathematics, physics, and even some tasks in accounting, law, or medicine.—
Jeremy Kahn,
Fortune,
21 Apr. 2026
-
The market said the confusion came from incorrect AI search results on apps like Google and Instagram.—
Rashad Alexander,
Kansas City Star,
20 Apr. 2026
Adjective
-
Now 43-38, Charlotte has lost ground this week with difficult losses to Boston and Detroit that followed the same blueprint, as the Hornets fell off a cliff in the fourth quarter at the wrong time.—
Scott Fowler,
Charlotte Observer,
11 Apr. 2026
-
Overfertilizing Fertilizing too much or at the wrong time could potentially damage plant roots, leading to leaf damage and eventual drop.—
Alexandra Jones,
The Spruce,
11 Apr. 2026
Cite this Entry
“Insidious.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/insidious. Accessed 25 Apr. 2026.
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